Latch tool

ABSTRACT

A latch tool for a wireline toolstring includes an anchor assembly that is attached to a support structure. A core assembly is configured for axial movement relative to the anchor assembly. The anchor assembly and the core assembly provide a spring chamber having a length that changes with axial movement of the core assembly. A spring opposes axial movement of the core assembly. A latch assembly includes at least one latching element that captures a coupling component. The spring provides a bias force that opposes axial movement of the core assembly in a latching direction, but permits axial movement of the core assembly in the latching direction when an axial force applied to the core assembly exceeds the bias force.

This application claims priority to PCT Patent Appln. No. PCT/GB2019/050728 filed Mar. 15, 2019, which claims priority GB Patent Appln. No. 1806838.7 filed Apr. 26, 2018, which are herein incorporated by reference.

BACKGROUND OF THE INVENTION 1. Technical Field

The present invention relates to a latch tool for use within a pressure control rig-up and wireline toolstring.

2. Background Information

A pressure control rig up is a package of assemblies that is used to extend the pressure containment of a wellbore to accommodate a wireline tool string.

A wireline toolstring is a package of one or more tools and/or instruments that is lowered into a wellbore for sensing/instrumentation and/or well bore manipulation purposes, particularly in the oil and gas production industry.

The wireline toolstring is lowered into the wellbore and retrieved by means of a wire and a winch. Upon retrieval of the toolstring to surface and reaching the top of the well the toolstring can be detached from the wire and removed.

If the winch is not stopped immediately the toolstring reaches the top of the well, the toolstring may come into contact with a stop that prevents further movement of the toolstring. The tension in the wire attached to the toolstring will then increase if the winch continues to operate. If the tension exceeds the yield strength of the wire, the wire may break allowing the toolstring to fall back down the well and potentially causing catastrophic damage to the toolstring and the wellbore, and a safety hazard to operators of the well.

To reduce this risk, it is known to provide a tool catcher device at the head of the well to secure a toolstring within a wireline rig up. However, known tool catcher devices do not operate automatically and require manual intervention to select either a catch mode or a release mode. Known tool catcher devices are not configured to operate according to the tension in the wire, and they cannot be adjusted to operate at different selectable tension values.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a latch tool (or bumper latch tool) that mitigates one or more of the aforesaid problems.

According to one aspect of the present invention there is provided a latch tool for a wireline toolstring having a coupling component attached to a wire. The latch tool may comprise an anchor assembly having a longitudinal axis and configured to be attached to a support structure. A core assembly may be connected to the anchor assembly and configured for axial movement relative to the anchor assembly. The anchor assembly and the core assembly may provide a spring chamber having an axial length that changes with axial movement of the core assembly. A spring may be located in the spring chamber and configured to oppose axial movement of the core assembly in a first axial direction. A latch assembly may be connected to the anchor assembly, the latch assembly including at least one latching element configured to capture a coupling component and prevent disengagement of the coupling component from the latch tool. The spring may provide a bias force that opposes axial movement of the core assembly in a latching direction, but permits axial movement of the core assembly in the latching direction when an axial force applied to the core assembly exceeds said bias force.

In an embodiment, the latch tool enables a coupling component to be captured, thus preventing a wireline toolstring from falling down a wellbore if the wire breaks. The latch tool may be configured to capture the coupling component automatically, when the tension applied to the wire exceeds a predetermined capture value. The latch tool may be configured so that it does not capture the coupling component when the tension applied to the wire is less than the predetermined capture value, so that it does not capture the coupling component unnecessarily. The latch tool may also be configured to provide a shock absorbing function, to slow a travelling toolstring gradually if it impacts the latch tool at speed when being lifted out of a wellbore, to reduce the risk of breaking the wire. The spring may be configured to provide a bias force that opposes engagement of a coupling component with the latch assembly, but that permits latching engagement of a coupling component with the latch assembly when an axial force applied to the core assembly by the coupling component exceeds a latching bias force provided by the spring. This helps to ensure that the latch tool captures the coupling component automatically when the tension applied to the wire exceeds a predetermined capture value, but does not capture the coupling component when the tension applied to the wire is less than the predetermined capture value, so that it does not capture the coupling component unnecessarily. This feature also enhances the shock absorbing function, so that it slows a travelling toolstring gradually if it impacts the latch tool at speed when being lifted out of a wellbore.

The length and/or the spring constant of the spring may be adjustable, allowing the latch tool to be modified according to factors such as the tensile strength of the wire and/or the mass of the toolstring.

The spring may comprise a plurality of disc springs, or any other suitable mechanical or pneumatic spring component, which may be configured to operate either in compression or tension.

The latch assembly may be configured for axial movement relative to the anchor assembly, for example to provide some free travel between the anchor assembly and the core assembly. This may assist removal of the coupling component from the latch tool after capture by providing limited free movement of the latching assembly without compressing the spring.

The latch assembly may be configured for axial movement relative to the anchor assembly over a first range of movement R1, and the core assembly may be configured for axial movement relative to the anchor assembly over a second range of movement R2, where R1<R2.

The latch assembly may comprise a plurality of latch elements that are resiliently biased towards a latching configuration. This feature may enhance automatic operation of the latch tool by avoiding the need for a control mechanism that controls operation of the latch elements.

The plurality of latch elements may comprise a plurality of resiliently deformable fingers, each finger carrying a latching formation at a free end of the finger.

Each latch element may comprise a cam surface that is engageable by the coupling component when in an unlatched configuration, and a latching surface that is engageable by the coupling component when in a latched configuration. The cam surface may be configured to allow the coupling component to engage the latching assembly automatically upon contacting the latch tool.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the invention will now be described, by way of example, with reference to the accompanying drawings, wherein:

FIG. 1 illustrates the components of a bumper latch assembly in side view and in side sectional view;

FIG. 2 is a sectional view showing a number of operational stages during attachment of the bumper latch tool to a rope socket;

FIG. 3 illustrates a side view and a sectional side view of the assembled bumper latch tool, and

FIG. 4 is a partially sectional side view of the bumper latch tool rigged up to the bottom of a stuffing box.

DETAILED DESCRIPTION OF THE INVENTION

The main components/assemblies of the bumper latch are shown in FIGS. 1 and 3. These include a substantially tubular anchor assembly 2 that has a longitudinal axis X. A core assembly 4 extends axially through the anchor assembly 2 and is mounted for sliding movement relative to the anchor assembly.

The anchor assembly 2 and the core assembly 4 together define a spring chamber 6 that extends parallel to the axis X and is located in the annular space between anchor assembly 2 and the core assembly 4. The upper end 6 a of the spring chamber 6 is defined by the anchor assembly 2 and the lower end 6 b is defined by the core assembly 4. The length L of the spring chamber 6 therefore changes as the core assembly 4 slides axially relative to the anchor assembly 2.

A compression spring 8 is located within the spring chamber 6 between the upper end 6 a and the lower end 6 b. In this embodiment the spring 8 comprises a plurality of disc springs (e.g. Belleville washers) 10 that are positioned in alternating orientations, so that the inner portion of each disc spring engages the inner portion of an adjacent disk spring on one side, and the outer portion of each disc spring engages the outer portion of an adjacent disc spring on the other side. Alternatively, some or all of the disc springs may be stacked in the same orientation. The disc springs can be made of any suitable resilient material, for example stainless steel.

The use of disc springs is advantageous, since it allows the uncompressed length of the spring 8 and/or the spring constant to be readily adjusted. For example, the uncompressed length of the spring can be adjusted by increasing or decreasing the number of disc springs, whereas the spring constant can be adjusted by changing the orientation of some of the disc springs. The use of disc springs can also provide a very high spring constant, for example in the region of 100,000 N/m. However, it should be understood that other types of springs or elastically compressible elements may also be used to form the compression spring 8. It is also possible by reconfiguring the structure of the bumper latch device, to replace the compression spring 8 with a tension spring or a hydraulically compressible element.

The bumper latch 1 also includes a latch assembly 12 that is mounted on the external cylindrical surface of the anchor assembly 2 and extends downwards beyond the lower end 2 a of the anchor assembly 2, and beyond the lower end 4 a of the core assembly 4. The latch assembly 12 is configured for axial sliding movement relative to the anchor assembly 2 in the direction of the longitudinal axis X. The latch assembly 12 has a plurality of latch elements 14 at the lower end 12 a of the latch assembly 12 for engaging a coupling component, for example a rope socket 16 (also called a fishneck or a spearhead) that is attached to the toolstring (not shown), as depicted in FIGS. 2 and 4.

The latch assembly is configured for axial movement relative to the anchor assembly over a first range of movement R1, and the core assembly connected is configured for axial movement relative to the anchor assembly over a second range of movement R2, where R1<R2.

The components that make up the anchor assembly 2, the core assembly 4 and the latch assembly 12 will now be described in more detail with particular reference to FIGS. 1 and 3.

The anchor assembly 2 comprises an anchor head 18, an anchor tube 20, a grub screw 22 and a locking ring 24. The anchor head 18 has an upper part 18 a with an external screw thread 26 and a lower part 18 b with an internal screw thread 28. A bore 30 extends axially through the anchor head 18, the bore having an upper part 30 a with a first diameter D1 and a lower part 30 b with a second diameter D2 that is larger than the first diameter D1. The upper and lower bore parts 30 a, 30 b are connected to one another by a radial face 32. A threaded transverse bore 34 extends through the lower part 18 b of the anchor head and accommodates the grub screw 22. The locking ring 24 is threadingly engaged with the external screw thread 26 provided on the upper part 18 a of the anchor head 18.

The anchor tube 20 is tubular and has an axial bore 21 with a substantially uniform internal diameter D3, which is greater than the diameter D1 of the upper anchor head bore 30 a. The anchor tube has an upper part 20 a with an external screw thread 36, a middle part 20 b and a lower part 20 c. The external diameter of the lower part 20 c is greater than that of the middle part 20 b, providing a radial face 38 at the junction of the middle and lower parts 20 b, 20 c. In the assembled anchor assembly 2 the external screw thread 36 is engaged with the internal screw thread 28 and the grub screw 22 is screwed into the transverse bore 34 to engage the upper part 20 a of the center tube, preventing disconnection of the anchor head 18 and the anchor tube 20.

The core assembly 4 comprises a center core 40 and a top nut 42. The center core 40 is tubular and has an upper part 40 a with an external diameter D5 and a lower part 40 b with an external diameter D6 that is greater than D5, providing a radial face 44 at the junction of the lower and upper parts 40 a, 40 b. A bore 46 of substantially uniform diameter extends axially through the center core 40. An external screw thread 48 is provided at an upper end of the center core 40, which is engaged by the top nut 42. The lower face 50 of the center core 40 has an inwards conical profile. The core assembly connected is configured for axial movement relative to the anchor assembly over a range of movement R2 between a lower position defined by engagement of the top nut 42 with the upper end of the anchor head 18 (as shown in FIG. 2, stage 1) and an upper position (not shown) defined either by engagement of the radial face 44 with the lower end of the anchor tube 20, or by the minimum length of the spring 8 when fully compressed preventing further axial movement of the center core 40.

The latch assembly 12 comprises a finger cone 52 and a top collar 54. The finger cone 52 comprises a cylindrical sleeve having an upper part 52 a and a lower part 52 b, the lower part 52 b being divided longitudinally into a number of resilient fingers 56 by longitudinal slots 58. An inwardly extended latch element 14 is provided at the lower end of each finger 56, each latch element 14 having an upper surface 14 a that is inclined inwards at a shallow angle (typically about 10 degrees) and a lower surface 14 b that is inclined inwards at a steeper angle (typically about 50 degrees). The lower surface 14 b comprises a cam surface that is engageable by the coupling component when in an unlatched configuration, and the upper surface 14 a comprises a latching surface that is engageable by the coupling component when in a latched configuration.

In this embodiment the radial thickness of each finger 56 increases towards the lower end of the finger to increase its stiffness. However, this feature is optional and may be omitted if not needed.

The upper part 52 a of the finger cone 52, which is not divided longitudinally is provided with an internal screw thread 60.

The top collar 54 has an upper part 54 a and a lower part 54 b that is provided with an external screw thread 62. In the assembled latch assembly 12 the external screw thread 62 of the top collar 54 engages the internal screw thread 60 of the finger cone 52, connecting the top collar 54 to finger cone 52. The lower end 54 b of the top collar 54 provides a radial face 64 that extends inwards from the surface of the finger cone 52.

In the assembled bumper latch 1, the spring chamber 6 is defined at its upper end by the radial face 32 between the upper and lower parts 18 a, 18 b of the anchor head, and at its lower end by the radial face 44 at the lower end 40 b of the center core 40. The length L of the spring chamber 6 is therefore equal to the axial distance between the two radial faces 32, 44. The length L of the spring chamber 6 changes as the core assembly 4 slides axially relatively to the anchor assembly 2, and the spring 8 is compressed between the radial faces, 32, 44 if the length L of the spring chamber is less than the unstressed length of the spring 8.

The latch assembly 12 is configured to slide axially relative to the anchor assembly 2 between a lower position defined by engagement of the radial face 64 at the lower end of the top collar 54 with the radial face 38 between the middle and lower parts 20 b, 20 c of the anchor tube 20, and an upper position defined by engagement of the upper end 54 a of the top collar with the lower part 18 b of the anchor head. Movement of the latch assembly 12 towards the upper position may also be opposed by compression of the spring 8 within the spring chamber 6, as upwards movement of the latch assembly 12 may cause upwards movement of the core assembly 4, owing to engagement of the latch elements 14 with the lower face 50 of the core assembly 4. The latch assembly is thus configured for axial movement relative to the anchor assembly over first range of movement R1 defined by the axial distance between the upper and lower positions as described above.

A typical installation for the bumper latch 1 is illustrated in FIG. 4. The bumper latch 1 is rigged up to the bottom of a stuffing box (not shown) and is positioned at the head of the wellbore 70. A toolstring (not shown) is attached to a rope socket 16, which is suspended by a wire rope 72. The rope 72 extends through the axial bore of the bumper latch 1 and then passes over a pulley 74 to a winch (not shown).

In use, the toolstring attached to the rope socket 16 may be lowered into the wellbore 70 and then hoisted out of the wellbore by winching in the rope 72. The bumper latch 1 is configured to capture the rope socket 16 when it is raised fully out of the wellbore 70, to prevent the toolstring falling back down the wellbore if the rope 72 breaks. The latch tool latch 1 is attached to a support structure 74 (for example the pressure control equipment) by screwing the external screw thread 26 of the anchor head 18 into a threaded bore in the support structure and then tightening the locking ring 24 against the lower face of the support structure to secure the anchor head in position.

Operation of the latch tool will now be described with reference to FIG. 2.

The first drawing in FIG. 2 shows the latch tool 1 in an inactive configuration. The core assembly 4 has fallen under gravity to its lowest position relative to the anchor assembly 2, and the length L of the spring chamber 6 is at its maximum value. In this embodiment the unstressed length of the spring 8 is less than the maximum length L of the spring chamber 6 and the spring is therefore uncompressed. The latch assembly 12 also falls under gravity to its lowest position relative to the anchor assembly 2.

The stages in an operation that results in engagement of a rope socket 16 with the latch tool 1 are shown consecutively in the next drawings, labelled stage 1, 2, 3, 4 and 5.

In stage 1, the rope socket 16, which is suspended by wire rope 72, is shown in a position in which it has been lifted to a point at which the upper end of the rope socket 16 just touches the lower end of the latch tool 1. In this embodiment the rope socket 16 has a conventional fish neck design comprising a substantially cylindrical tubular body 80, which has an arrow shaped 82 at its upper end. The diameter of the head 82 is greater than that of the body 80, providing an annular latching face 84 at the lower end of the head 82. This annular latching face 84 may optionally be inclined downwards (raked), and provides a shoulder that can be engaged by the upper latching faces 14 a of the latch assembly 12.

In stage 2 the rope socket 16 has been lifted slightly higher by means of the rope 72. The head 82 engages the lower ends of the core assembly 8 and the latch assembly 12, lifting both assemblies upwards relative to the anchor assembly 2. As the core assembly 4 is lifted the length L of the spring chamber 6 decreases, bringing the spring 8 into contact with the upper and lower ends of the spring chamber 6. The upper end of the latch assembly 12 has also been brought into engagement with the annular face at the lower end 18 b of the anchor head 18, which prevents further upwards movement of the latch assembly 12.

In stage 3 the rope socket 16 has been lifted still further relative to the anchor assembly 2. The latch assembly 12 cannot rise any higher as further movement is prevented by engagement with the underside of the anchor head 18. The head 82 of the rope socket 16 presses against the lower cam surface 14 b and spreads apart the fingers 56 of the latch assembly 12, allowing the head 82 to penetrate the latch assembly 12. The rope socket 16 also pushes the core assembly 4 further upwards, compressing the spring 8 within the spring chamber 6. The compression of the spring 8 provides a force that opposes further upwards movement of the rope socket 16.

In stage 4 the rope socket 16 has been lifted still further against the force provided by the compressed spring 6, to a point where the latching face 84 at the lower end of the head 82 has progressed passed the upper latching face 14 a of the latch assembly 12.

This allows the fingers 12 to spring inwards towards the body 80 of the rope socket, so that the latching surface 14 a engages the annular latching face 84 at the lower end of the head 82. This prevents disengagement of the rope socket 16 from the latch tool 1.

In stage 5, the latch tool 1 is shown in a configuration in which it is supporting the rope socket 16, for example following failure of the wire rope 72. The head 82 of the rope socket is supported by the latch elements 14 provided that the lower end of the latch assembly 12, and the latch assembly 12 is itself supported by its engagement with the radial face 38 of the anchor tube 20. The anchor tube 20 and the latch assembly 12 have moved downwards under gravity, thus releasing the compression of the spring 8.

The latch tool described above comprises only an exemplary embodiment of the invention. Various modifications of the invention are of course possible as described herein and as will be apparent to a person of ordinary skill in the art. 

What is claimed is:
 1. A latch tool for capturing a wireline toolstring having a coupling component attached to a wire, the latch tool comprising: an anchor assembly having a longitudinal axis and configured to be attached to a support structure; a core assembly connected to the anchor assembly and configured for axial movement relative to the anchor assembly, the anchor assembly and the core assembly providing a spring chamber having an axial length that changes with axial movement of the core assembly; a spring located in the spring chamber and configured to be deformed by axial movement of the core assembly relative to the anchor assembly; and a latch assembly connected to the anchor assembly, the latch assembly including at least one latching element configured to capture a coupling component when the coupling component moves in an axial latching direction relative to the latch assembly from an unlatched position to a latched position, and to prevent subsequent disengagement of the coupling component from the latch tool; wherein the core assembly is configured to engage the coupling component during movement of the coupling component from the unlatched position to the latched position, and wherein the spring provides a bias force that acts on the core assembly and opposes axial movement of the core assembly in the latching direction, but permits axial movement of the core assembly in the latching direction when an axial force applied to the core assembly by the coupling component exceeds said bias force.
 2. The latch tool according to claim 1, wherein the spring is configured to provide a bias force that opposes engagement of a coupling component with the latch assembly, but permits latching engagement of a coupling component with the latch assembly when an axial force applied to the core assembly by the coupling component exceeds a latching bias force provided by the spring.
 3. The latch tool according to claim 1, wherein the length and/or the spring constant of the spring is adjustable.
 4. The latch tool according to claim 3, wherein the spring comprises a plurality of disc springs.
 5. The latch tool according to claim 1, wherein the latch assembly is configured for axial movement relative to the anchor assembly.
 6. The latch tool according to claim 5, wherein the latch assembly is configured for axial movement relative to the anchor assembly over a first range of movement R1, and the core assembly is configured for axial movement relative to the anchor assembly over a second range of movement R2, where R1<R2.
 7. The latch tool according to claim 1, preceding claims, wherein the latch assembly comprises a plurality of latch elements that are resiliently biased towards a latching configuration.
 8. The latch tool according to claim 7, wherein the plurality of latch elements comprise a plurality of resiliently deformable fingers, each finger carrying a latching formation at a free end of the finger.
 9. The latch tool according to claim 7, wherein each latch element comprises a cam surface that is engageable by the coupling component when in an unlatched configuration, and a latching surface that is engageable by the coupling component when in a latched configuration.
 10. The latch tool according to claim 8, wherein each latch element comprises a cam surface that is engageable by the coupling component when in an unlatched configuration, and a latching surface that is engageable by the coupling component when in a latched configuration.
 11. A latch tool for capturing a wireline toolstring having a coupling component attached to a wire, the latch tool comprising: an anchor assembly having a longitudinal axis and configured to be attached to a support structure; a core assembly connected to the anchor assembly and configured for axial movement relative to the anchor assembly, the anchor assembly and the core assembly providing a spring chamber having an axial length that changes with axial movement of the core assembly; a spring located in the spring chamber and configured to be deformed by axial movement of the core assembly relative to the anchor assembly; and a latch assembly connected to the anchor assembly, the latch assembly including at least one latching element configured to capture a coupling component when the coupling component moves in a latching direction towards the latch assembly from an unlatched position to a latched position, and to prevent subsequent disengagement of the coupling component from the latch tool; wherein the core assembly is configured to engage the coupling component during movement of the coupling component from the unlatched position to the latched position, and wherein the spring provides a bias force that acts on the core assembly and opposes axial movement of the core assembly in the latching direction, but permits axial movement of the core assembly in the latching direction when an axial force applied to the core assembly by the coupling component exceeds said bias force.
 12. A latch tool for capturing a wireline toolstring having a coupling component attached to a wire, the latch tool comprising: an anchor assembly having a longitudinal axis and configured to be attached to a support structure; a core assembly connected to the anchor assembly and configured for axial movement relative to the anchor assembly, the anchor assembly and the core assembly providing a spring chamber having an axial length that changes with axial movement of the core assembly; a spring located in the spring chamber and configured to be deformed by axial movement of the core assembly relative to the anchor assembly; and a latch assembly connected to the anchor assembly, the latch assembly including at least one latching element configured to capture a coupling component when the coupling component moves in a latching direction towards the latch assembly from an unlatched position to a latched position, and to prevent subsequent disengagement of the coupling component from the latch tool; wherein the core assembly is configured to engage the coupling component during movement of the coupling component from the unlatched position to the latched position; wherein the spring provides a bias force that acts on the core assembly and opposes axial movement of the core assembly in the latching direction, but permits axial movement of the core assembly in the latching direction when an axial force applied to the core assembly by the coupling component exceeds said bias force; and wherein the latch assembly is configured for axial movement relative to the anchor assembly. 